Go to hell and back to get valid frames off the wire, and keep track of error counts

include/patty/kiss.h

@@ -31,6 +31,8 @@ patty_kiss_tnc *patty_kiss_tnc_open(const char *device, size_t bufsize);
 
 void patty_kiss_tnc_close(patty_kiss_tnc *tnc);
 
+int patty_kiss_tnc_errors(patty_kiss_tnc *tnc);
+
 ssize_t patty_kiss_tnc_recv(patty_kiss_tnc *tnc,
     void **frame, int *port);
 

src/kiss.c

@@ -17,6 +17,7 @@ enum kiss_flags {
 
 struct _patty_kiss_tnc {
     int    fd;
+    int    errors;
     void * frame;
     void * buf;
     size_t bufsz;
@@ -42,6 +43,7 @@ patty_kiss_tnc *patty_kiss_tnc_open(const char *device, size_t bufsz) {
         goto error_open;
     }
 
+    tnc->errors = 0;
     tnc->bufsz  = bufsz;
     tnc->buflen = 0;
 
@@ -113,7 +115,7 @@ static ssize_t tnc_decode(patty_kiss_tnc *tnc, void *frame, size_t *len, int *po
          * Not all KISS TNCs will emit a type byte at the start of a frame
          * to the host; if the low nybble has a value of zero, then presume
          * the high nybble to be the radio port number from which the
-         * packet originated.
+         * frame originated.
          */
         if (i == 1 && (c & 0x0f) == 0) {
             *port = (c & 0xf0) >> 4;
@@ -180,6 +182,18 @@ error_io:
     return -1;
 }
 
+static void tnc_drop(patty_kiss_tnc *tnc) {
+    memset(tnc->buf,   '\0', tnc->bufsz);
+    memset(tnc->frame, '\0', tnc->bufsz);
+
+    tnc->buflen = 0;
+    tnc->errors++;
+}
+
+int patty_kiss_tnc_errors(patty_kiss_tnc *tnc) {
+    return tnc->errors;
+}
+
 static void tnc_flush(patty_kiss_tnc *tnc, size_t len) {
     /*
      * Move everything from the buffer not processed up to this point, to the
@@ -195,35 +209,42 @@ static void tnc_flush(patty_kiss_tnc *tnc, size_t len) {
 }
 
 ssize_t patty_kiss_tnc_recv(patty_kiss_tnc *tnc, void **frame, int *port) {
-    ssize_t decoded;
+    ssize_t buffered, decoded;
      size_t framelen;
 
-    /*
-     * Fill the buffer with something to parse!
-     */
-    if (tnc_buffer(tnc) < 0) {
-        goto error_io;
-    }
-
     /*
      * Initialize the frame to be returned to the caller.
      */
     memset(tnc->frame, '\0', tnc->bufsz);
 
+    do {
         /*
-     * Try to decode the TNC buffer into the packet.
+         * Fill the buffer with something to parse.
+         */
+        if ((buffered = tnc_buffer(tnc)) < 0) {
+            goto error_io;
+        }
+
+        /*
+         * Try to decode the TNC buffer into the frame.
          */
         if ((decoded = tnc_decode(tnc, tnc->frame, &framelen, port)) < 0) {
             goto error_io;
         }
 
         /*
-     * If we have decoded frame data, then flush the buffer up to the point of
+         * If we can no longer buffer nor decode any data, then drop the whole
-     * the next frame start, if present.
+         * frame.
          */
-    if (decoded) {
+        if (decoded == 0 && buffered == 0) {
-        tnc_flush(tnc, decoded);
+            tnc_drop(tnc);
         }
+    } while (decoded == 0);
+
+    /*
+     * Flush the buffer up to the point of the next frame start.
+     */
+    tnc_flush(tnc, decoded);
 
     *frame = tnc->frame;